General Description
The MAX1725/MAX1726 are ultra-low supply current,
low-dropout linear regulators intended for low-power
applications that demand the longest possible battery
life. Unlike inferior PNP-based designs, the MAX1725/
MAX1726s' PMOS pass elements maintain an ultra-low
2A supply current throughout their entire operating
range and in dropout. Despite their ultra-low power
consumption, the MAX1725/MAX1726 have tight output
accuracy (1.5%) and require just 1F output capacitance
to achieve good load-transient response.
These regulators have a wide input voltage range
(+2.5V to +12V), making them excellent choices for
systems powered from two lithium-ion (Li+) cells and 9V
batteries. Other features include reverse-battery protec-
tion, short-circuit protection, and thermal protection.
The MAX1725 provides an adjustable 1.5V to 5V output
using an external resistor-divider. The MAX1726 pro-
vides factory preset 1.8V, 2.5V, 3.3V, or 5V output volt-
ages (see the Ordering Information). Both devices are
available in a tiny 5-pin SOT23 package.
________________________Applications
Smoke Detectors
Remote Transmitters
Smart Battery Packs
Industrial Control Systems
Microcontroller Power
Real-Time Clock Backup Power
PDAs and Handy-Terminals
Battery-Powered Alarms
Features
o 2A Supply Current
o Reverse-Battery Protection
o +2.5V to +12V Input Voltage Range
o Fixed 1.8V, 2.5V, 3.3V, and 5V Output Voltages
(MAX1726)
o Adjustable 1.5V to 5V Output Voltages (MAX1725)
o 20mA Guaranteed Output Current
o 1.5% Output Voltage Accuracy
o Small 1F Output Capacitor
o Short-Circuit Protection
o Thermal Protection
o Tiny 5-Pin SOT23 Package
MAX1725/MAX1726
12V, Ultra-Low I
Q
, Low-Dropout
Linear Regulators
________________________________________________________________ Maxim Integrated Products
1
V
IN
2.5V TO 12V
OUTPUT
1.5V TO 5V
MAX1726
OFF
ON
IN
OUT
SHDN
GND
Typical Operating Circuit
19-1680; Rev 1; 2/03
Ordering Information
Selector Guide
Pin Configuration appears at end of data sheet.
Note: See the Selector Guide for the MAX1725/MAX1726 output
options as they relate to the part number suffix.
5 SOT23-5
PIN-
PACKAGE
TEMP RANGE
-40C to +85C
MAX1725EUK-T
PART
5 SOT23-5
-40C to +85C
MAX1726EUK18-T
5 SOT23-5
-40C to +85C
MAX1726EUK25-T
5 SOT23-5
-40C to +85C
MAX1726EUK33-T
5 SOT23-5
-40C to +85C
MAX1726EUK5-T
ADNK
TOP
MARK
ADNL
ADNM
ADNN
ADNO
OUTPUT VOLTAGE
(V)
PART
Adj 1.5 to 5.0
MAX1725EUK-T
Fixed 1.8
MAX1726EUK18-T
Fixed 2.5
MAX1726EUK25-T
Fixed 3.3
MAX1726EUK33-T
Fixed 5.0
MAX1726EUK50-T
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1725/MAX1726
12V, Ultra-Low I
Q
, Low-Dropout
Linear Regulators
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= V
OUT
+ 1V, SHDN = IN, I
OUT
= 1mA, T
A
= -40C to +85C, unless otherwise noted. Typical values are at
T
A
= +25C.) (Note 1)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN to GND ................................................................-14V to +14V
SHDN to GND..............................................-0.3V to (V
IN
+ 0.3V)
(-0.3V to + 0.3V when V
IN
< 0V)
OUT, FB (MAX1725 only) to GND...................-0.3V to +6V when
V
IN
>5.7V; -0.3V to (V
IN
+ 0.3V) when 0V <
V
IN
< 5.7V; -0.3V to +0.3V when V
IN
< 0V
OUT Continuous Current...................................................200mA
OUT Short Circuit...........................................................Indefinite
Continuous Power Dissipation (T
A
= +70C)
5-Pin SOT23-5 (derate 7.1mW/C above +70C) ........571mW
JA
...............................................................................+140C/W
Junction Temperature ......................................................+150C
Operating Temperature Range ...........................-40C to +85C
Storage Temperature Range .............................-65C to +150C
Lead Temperature (soldering, 10s) .................................+300C
SHDN = 0V, V
IN
= 12V, V
OUT
= 0V
V
IN
= 12V
(Note 2)
V
IN
= -12V, V
SHDN
= 0V
V
IN
= 2.5V to 12V
V
IN
= 12V, V
OUT
= 0V
V
FB
= 1.25V
I
OUT
= 20mA for V
OUT
2.5V, I
OUT
= 10mA for
V
OUT
< 2.5V, not applicable for V
OUT
< 1.9V
V
IN
= (V
OUT
+ 1V) or 3V (Note 4)
MAX1725 only
V
IN
= 2.5V or (V
OUT
+ 0.5V) to 12V
I
OUT
= 1mA to 20mA, V
IN
= (V
OUT
+ 1V)
or 3V (min)
V
SHDN
= 0V to 12V
CONDITIONS
C
15
Thermal-Shutdown Hysteresis
A
0.01
10
IN Reverse Leakage Current
1.5
nA
-20
2
+20
I
FB
FB Input Bias Current
(MAX1725 only)
0.1
nA
-50
+50
I
SHDN
SHDN Input Bias Current
A
0.7
2
I
IN(SHDN)
Shutdown Supply Current
A
2
4.5
I
IN
V
2.5
12
V
IN
Input Voltage Range
Supply Current
V
2
V
IH
mA
40
I
SC
Foldback Current Limit
mV
300
600
V
DO
Dropout Voltage (Note 4)
mA
20
80
I
OUT
Maximum OUT Current
V
1.5
5
V
OUT
OUT Voltage Range
%
-1.5
1.5
OUT Voltage Accuracy (Note 3)
%/V
0.01
0.3
V
LNR
Line Regulation
%/mA
0.015
0.15
V
LDR
Load Regulation
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
T
A
= +25C
T
A
= +85C
T
A
= +25C
T
A
= +85C
MAX1725 only (Note 3)
V
1.245
V
FB
FB Voltage
-2
+2
-3
+3
T
A
= +25C
T
A
= 0C to +85C
T
A
= -40C to +85C
0.5
V
IL
SHDN Input Threshold
Temperature rising
C
150
Thermal-Shutdown Threshold
MAX1725/MAX1726
12V, Ultra-Low I
Q
, Low-Dropout
Linear Regulators
_______________________________________________________________________________________
3
0
1
3
2
4
5
4
6
7
5
8
9
10
11
12
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1725/26 toc01
INPUT VOLTAGE (V)
SUPPLY CURRENT (
A)
0
1
3
2
4
5
SUPPLY CURRENT vs. LOAD CURRENT
MAX1725/26 toc02
LOAD CURRENT (mA)
SUPPLY CURRENT (
A)
0
10
5
15
20
V
IN
= 5V
0
3
2
1
4
5
-40
0
20
-20
40
60
80
SUPPLY CURRENT vs. TEMPERATURE
MAX1725/26 toc03
TEMPERATURE (
C)
SUPPLY CURRENT (
A)
V
IN
= 5V
-1.4
-1.0
-0.4
-0.6
-0.2
0
4
6
7
5
8
9
10
11
12
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1725/26 toc04
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (%DEVIATION)
-0.8
-1.2
I
LOAD
= 20mA
I
LOAD
= 1mA
NOMINAL OUTPUT = 3.3V
-0.8
-0.4
0.2
-0.2
0.6
0.8
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1725/26 toc05
LOAD CURRENT (mA)
OUTPUT VOLTAGE (% DEVIATION)
0
4
2
6
20
0.4
0
-0.6
8
10 12 14
16 18
NOMINAL OUTPUT = 3.3V
V
IN
= 4.5V
-0.30
-0.10
0.10
0
0.20
0.30
-40
0
-20
20
40
60
80
NORMALIZED OUTPUT VOLTAGE
vs. TEMPERATURE
MAX1725/26 toc06
TEMPERATURE (
C)
NORMALIZED OUTPUT VOLTAGE (%) -0.20
I
OUT
= 1mA
Typical Operating Characteristics
(V
OUT
= +3.3V, I
OUT
= 1mA, T
A
= +25C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= V
OUT
+ 1V, SHDN = IN, I
OUT
= 1mA, T
A
= -40C to +85C, unless otherwise noted. Typical values are at
T
A
= +25C.) (Note 1)
Note 1: Limits are 100% production tested at +25C. All temperature limits are guaranteed by design.
Note 2: Guaranteed by OUT line-regulation testing.
Note 3: OUT accuracy from nominal voltage. The MAX1725 is tested at V
OUT
= 1.5V, 2.5V, and 5V.
Note 4: When V
OUT
falls to 4% below its value at V
IN
= V
OUT
+ 1V.
I
OUT
from 1mA to 10mA, t
R
= t
F
= 1s
V
IN
= 0.25V, t
R
= t
F
= 5s
f = 10Hz to 100kHz
CONDITIONS
mV
200
OUT Load-Transient
Overshoot/Undershoot
mV
15
OUT Line-Transient
Overshoot/Undershoot
V
RMS
350
e
n
OUT Noise
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
Detailed Description
The MAX1725/MAX1726 are low-dropout, low-quiescent-
current linear regulators designed primarily for battery-
powered applications (Figure 1). The MAX1725 provides
an adjustable output voltage from 1.5V to 5V using an
external resistor-divider. The MAX1726 supplies preset
output voltages of 1.8V, 2.5V, 3.3V, or 5V. These devices
consist of a +1.245V error amplifier, MOSFET driver,
and P-channel pass transistor (Figure 2).
MAX1725/MAX1726
12V, Ultra-Low I
Q
, Low-Dropout
Linear Regulators
4
_______________________________________________________________________________________
Typical Operating Characteristics (continued)
(V
OUT
= +3.3V, I
OUT
= 1mA, T
A
= +25C, unless otherwise noted.)
NAME
MAX1725 MAX1726
1
1
IN
2
2
GND
3
3
OUT
--
4
GND
4
--
FB
Pin Description
FUNCTION
Supply Voltage Input
Ground
Voltage Output
Ground
Feedback Voltage Input
5
5
SHDN
Active-Low Shutdown Input
PIN
I
OUT
20mA/div
V
OUT
100mV/div
400
s/div
LOAD TRANSIENT
MAX1725/26 toc10
C
OUT
= 1
F
I
OUT
= 1mA - 20mA
V
SHDN
2V/div
V
OUT
1V/div
4ms
TURN-ON/TURN-OFF RESPONSE
MAX1725/26 toc11
C
OUT
= 1
F
I
OUT
= 1mA
0
100
50
200
150
250
300
0
10
5
15
20
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX1725/26 toc07
LOAD CURRENT (mA)
DROPOUT VOLTAGE (mV)
T
A
= +85C
T
A
= +25C
T
A
= -40C
80
70
60
50
40
30
20
10
0
0.01
1
10
0.1
100
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX1725/26 toc08
FREQUENCY (kHz)
PSRR (dB)
V
IN
= 5V
V
OUT
= 3.3V
R
L
= 3.3k
C
OUT
= 1
F
V
IN
200mV/div
V
OUT
20mV/div
100
s/div
LINE-TRANSIENT RESPONSE
MAX1725/26 toc09
C
OUT
= 1
F
I
OUT
= 1mA
The error amplifier compares 1.245V to the selected
feedback voltage and amplifies the difference. If the
feedback voltage is lower than 1.245V, the pass-tran-
sistor gate is pulled lower, allowing more current to
pass, and thus increasing the output voltage. If the
feedback voltage is higher than 1.245V, the pass-tran-
sistor gate is driven higher, allowing less current to
pass to the output. The output voltage is fed back
through either an internal resistor voltage-divider con-
nected to OUT (MAX1726) or an external resistor net-
work connected to FB (MAX1725). Additional features
include an output current limiter, reverse-battery protec-
tion, a thermal sensor, and shutdown logic.
Internal P-Channel Pass Transistor
The MAX1725/MAX1726 feature a P-channel MOSFET
pass transistor. This provides advantages over similar
designs using PNP pass transistors, including longer
battery life. The P-channel MOSFET requires no base
drive, which reduces quiescent current considerably.
PNP-based regulators waste considerable current in
dropout when the pass transistor saturates; they also
use high base-drive currents under large loads. The
MAX1725/MAX1726 do not suffer from these prob-
lems, and consume only 2A of quiescent current
throughout their load range (see the Typical Operating
Characteristics).
Shutdown
To enter shutdown, drive the SHDN pin below 0.5V.
When the MAX1725/MAX1726 are shut down, the output
MAX1725/MAX1726
12V, Ultra-Low I
Q
, Low-Dropout
Linear Regulators
_______________________________________________________________________________________
5
INPUT
2.5V TO 12V
OUTPUT
1.5V TO 5V
MAX1725
OFF
ON
IN
OUT
FB
SHDN
GND
R1
R2
1.2M
C
OUT
1
F
C
IN
1
F
IN
OUT
FB (MAX1725 ONLY)
(MAX1726 ONLY)
SHDN
BIAS
CIRCUITRY
THERMAL
SHUTDOWN
GND
1.245V
MAX1725
MAX1726
Figure 1. Typical Application Circuit
Figure 2. Functional Diagram
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